UNIVERSITY    OF    CALIFORNIA        AGRICULTURAL  EXPERIMENT  STATION 

BENJ.    IDE    WHEELER,    PRESIDENT 

COLLEGE    OF    AGRICULTURE 

WWLLtVI6     WF     «««'^w'-'  ""=■  THOMAS    FORSYTH    HUNT,  Dean  and  Director 

BERKELEY  H"     E*     VAN      NORMAN'     VICE-DIRECTOR    AND    DEAN 

University  Farm  School 


CIRCULAR  No.  US 
(March,  3916) 

"LUNGWORMS" 

A  PRELIMINARY  REPORT  ON  TREATMENT,  WITH  SOME 

OBSERVATIONS  REGARDING  THE  EPIDEMIOLOGY 

AND  LIFE  HISTORY  OF  THE  PARASITE 

By  WILLIAM  B.  HEBMS  and  STANLEY  B.  FREEBORN 


Introduction. — During  the  last  few  years  a  disease  known  as 
"  lungworms, "  verminous  bronchitis,  or  pulmonary  strongylosis,  has 
become  a  problem  of  distinct  importance  to  California  stockmen.  This 
disease  is  caused  by  thread-like  worms  which  infest  the  tracheae, 
bronchi,  and  bronchioles  (air  passages  of  the  lungs).  Calves,  goats 
and  swine  are  the  chief  hosts  of  these  parasites. 

The  three  species  of  lungworms  which  are  of  economic  importance 
belong  to  the  sub-family  Metastronglinae  of  the  class  Nematoda,  and 
were  previously  all  included  under  the  genus  Strongylus.  This  genus 
has  been  divided,  so  that  at  the  present  time,  the  three  species  are 
known  as  Dictyocaulus  viviparous  (Bloch)  affecting  calves,  deer  and 
rarely  sheep;  Dictyocaulus  filaria  (Rudolphi)  affecting  sheep,  goats, 
camels,  deer  and  sometimes  calves ;  and  lastly  Metastrongylus  apri 
(Gmelin),  the  corresponding  parasite  of  swine.  The  adult  worms  of 
these  three  species  are  very  similar  in  structure,  differing  mainly  in 
size. 

The  above  named  species  are  the  only  ones  that  have  come  to  the 
attention  of  the  Parasitology  Laboratory  of  the  Experiment  Station 
and  although  there  are  tAVO  others  associated  with  domestic  animals, 
D.  arnfieldi  (Cobbold)  infecting  horses  and  asses,  and  Metastrongylus 
brevivaginatus  (Raillet  and  Henry)  affecting  pigs,  it  is  doubtful  if 
they  occur  in  California.  These  five  parasites  complete  the  list  of 
nematodes  of  economic  importance  infesting  the  bronchi  and  bron- 
chioles exclusively  during  their  adult  life,  but  two  other  genera  of 
nematodes,  Synthetocaulus  and  Haemo  strongylus,  are  sometimes  pres- 
ent in  the  lungs, — the  former  in  the  lung  tissue  and  the  latter  in  the 
pulmonary  artery. 


The  lung  worm  of  calves,  Dictyocaulus  viviparous,  is  a  slender, 
whitish,  thread-like  worm.  The  male  is  about  one  and  one  half  inches 
long  and  the  female  varies  from  two  and  a  half  to  three  and  a  quarter 
inches. 

Dictyocaulus  filaria,  the  lungworm  of  sheep  and  goats,  is  the  larg- 
est of  the  three,  ranging  from  two  and  a  half  to  three  inches  in  length 
in  the  case  of  the  male,  while  the  female  is  sometimes  three  and  a 
half  to  four  inches  long. 

Metastrongylus  apri,  found  in  swine,  is  much  smaller  than  either  of 
the  others  described.  The  male  is  scarcely  three  quarters  of  an  inch 
in  length  and  the  female  rarely  exceeds  two  inches. 

"While  the  parasites  themselves  often  cause  the  death  of  the  animals 
by  suffocation,  their  chief  danger  lies  in  the  fact  that  an  infested 
animal  is  an  easy  victim  to  pathogenic  organisms  because  of  the 
unnatural  condition  of  the  lungs  due  to  the  worms.  The  worms,  when 
present  in  great  numbers,  often  cause  the  collapse  of  portions  of  the 
lung  tissue  by  blocking  the  bronchi,  which  supply  air  to  those  por- 
tions, thus  producing  favorable  media  for  the  development  of  bacteria. 
Broncho-penumonia,  so  often  associated  with  an  infestation  of  lung- 
worms,  undoubtedly  owes  its  origin  to  this  circumstance. 

Symptoms. — The  animals  affected  invariably  have  a  more  or  less 
violent  cough,  hard  at  first  but  becoming  softer  and  occurring  in 
paroxysms ;  frothing  at  the  mouth  may  also  be  noted  sometimes.  The 
animals  stand  or  lie  with  their  necks  extended  and  in  pronounced 
cases  they  are  noticed  to  breathe  with  difficulty.  They  are  generally 
extremely  weak  and  short  of  breath,  falling  to  their  knees  if  hurried 
in  the  drive.  The  temperature  varies  but  does  not  become  exceedingly 
high.  These  form,  perhaps,  all  the  clinical  symptoms  that  can  be 
given  and  unlike  many  parasitic  infestations,  all  the  symptoms  are 
generally  present. 

The  exception  must  be  made,  however,  in  the  case  of  swine.  The 
symptoms  here  are,  if  noticeable  at  all,  never  accentuated  and  a  post- 
mortem examination  is  generally  necessary  to  confirm  a  diagnosis  of 
"lungworTUS." 

Treatment. — It  has  been  the  common  practice  among  some  stock 
raisers  when  an  infestation  of  lungworms  occurs  to  subject  those  ani- 
mals which  they  believed  would  succumb  to  the  ravages  of  the  parasite, 
if  untreated,  to  a  treatment  consisting  of  inhaling  the  dust  of  air 
slacked  lime  or  sulphur  fumes.  This  heroic  treatment  generally  re- 
sulted in  saving  a  few  of  the  animals,  but  the  majority  usually  suc- 
cumbed under  treatment.  However,  the  rancher  reasoned  that  to  save 
a  few  was  better  than  losing  them  all. 


Lungs  of  a  goat,  showing  the  lungworms  in  the  trachea. 


With  this  idea  in  mind,  that  it  might  be  possible  to  have  the  in- 
fested animal  breathe  vapors  or  liquids  that  would  destroy  the  worms 
and  leave  the  animal  unaffected,  Mr.  E.  M.  Ledyard,  a  graduate 
student,  started  a  series  of  experiments  under  the  direction  of  the 
senior  author,  to  ascertain  what  remedies  might  safely  be  used  in  this 
way.  Various  chemicals,  including  turpentine,  benzine,  chloroform 
and  other  substances  were  used  separately  and  in  various  combina- 
tions. The  method  of  administering  the  doses  was  varied  by  trying 
both  nasal  and  tracheal  injections. 

The  result  of  these  tests  proved  that  pure  chloroform  administered 
in  each  nostril  by  means  of  a  pipette  was  most  effective.  The  amount 
administered  to  each  animal  must  needs  be  a  variable  quantity,  de- 
pending upon  the  age,  resistance  and  general  condition  of  the  indi- 
vidual animal.  Among  the  first  animals  treated  was  a  herd  of  150 
angora  goats.  In  the  fall  of  3  914,  Mr.  Ledyard  and  the  junior  author 
successfully  treated  these  with  one  and  a  half  cubic  centimeters  of 
chloroform  in  each  nostril,  thus  totaling  three  cubic  centimeters  per 
animal.  In  every  instance  the  animal  became  slightly  anaesthetized 
for  a  period  varying  from  two  to  twenty  minutes,  but  no  bad  results 
developed  in  the  herd,  which  after  two  more  treatments  became  ap- 
parently free  from  lungworms. 

At  that  time  it  was  supposed  that  the  chloroform  actually  hilled 
the  lungworms  in  situ  and  that  they  were  eliminated  by  coughing. 
Later  developments,  however,  show  that  the  chloroform  merely  stupe- 
fies the  worms  and  at  the  same  time  irritates  the  throat  and  windpipe, 
thus  causing  a  prolonged  paroxysm  of  coughing  during  which  the 
worms  are  coughed  up  and  swallowed. 

In  the  first  experiments  it  was  attempted  to  find  a  standard  dose 
of  chloroform  that  could  be  recommended  to  the  rancher  with  assur- 
ance of  safety  and  effectiveness.  Later  experiments  have  proved  the 
impossibility  of  this,  for  one  animal  has  been  found  to  require  five 
times  the  amount  of  chloroform  needed  to  produce  the  same  effect  in 
another. 

This  variability  has  led  to  our  present  practice  of  administering 
enough  chloroform  (within  certain  limits)  to  make  the  treated  animal 
slightly  ' '  groggy. ' '  The  maximum  dosage  has  been  eleven  cubic  centi- 
meters for  calves  and  three  cubic  centimeters  for  goats. 

The  animals  to  be  treated  should  be  confined  in  a  corral  which  is 
free  from  grass  and  other  vegetation.  The  chloroform  is  best  admin- 
istered by  tipping  back  the  animal's  head  and  injecting  the  desired 
dose  of  chloroform  with  a  small  pipette  (an  ordinary  fountain  pen 
filler  will  be  found  satisfactory).     Half  the  dose  is  administered  in 


each  nostril.  The  action  of  the  chloroform  is  enhanced  by  stopping 
the  nostrils  with  the  hand  or  cotton  plugs  for  a  few  moments  after 
injection. 

Two  hours  after  the  treatment  a  saline  purge  of  Epsom  or  Glau- 
ber's salts  should  be  given  the  animals.  Feces  should  be  carefully  dis- 
infected by  frequent  and  liberal  sprinklings  with  chloride  of  lime. 

Feed  and  watering  troughs  should  be  so  constructed  in  the  corral 
that  pollution  with  feces  will  be  impossible.  Treatments  should  be  con- 
tinued at  intervals  of  three  to  five  days  until  the  animals  improve. 
Three  treatments  is  the  maximum  number  that  we  have  needed  to  use 
in  any  of  our  experiments. 

In  England,  where  chloroform  is  the  chief  anaesthetic,  many  cases 
of  necrosis  of  the  liver  have  resulted  from  prolonged  chloroform 
anaesthesia.  This  problem  naturally  led  to  some  hesitation  in  suggest- 
ing the  above  method  of  chloroform  treatment  for  lungworms,  but 
several  post-mortem  examinations  of  treated  animals  which  revealed 
perfectly  healthy  livers  seem  to  discount  the  danger. 

Life  History. — The  life  history  of  these  parasites  has  never  been 
entirely  worked  out  and  it  is  only  within  the  last  few  years  that  any 
valuable  contributions  have  been  made  to  the  subject. 

Early  in  our  investigations  we  observed  that  the  embryos  found  in 
the  lungs  were  of  two  distinct  types.  Our  first  thought  was  that  these 
might  be  embryos  of  two  different  species  of  lungworms,  but  this  was 
discounted  by  the  fact  that  we  could  find  but  one  species  of  adults  in 
the  lungs.  That  the  differentiation  might  be  due  to  sex  was  rejected 
owing  to  the  fact  that  the  types  differed  not  only  in  shape  and  struc- 
ture, but  also  in  their  movements,  location  and  habits.  Thus  the 
theory  gained  belief  that  these  two  types  were  designed  to  maintain 
a  free-living  and  a  parasitic  generation.  This  belief  was  confirmed  by 
Doctor  von  Linden1  of  the  University  of  Bonn,  who  found  that  in  the 
mucus  of  the  trachea  and  of  the  space  behind  the  nose  there  were  slim, 
strong-moving  embryos  that  were  capable  of  living  outside  the  body. 
In  the  lungs  the  embryos  were  short,  thick,  slow  moving,  and  unable 
to  live  outside  the  body. 

Dr.  von  Linden  found  that  if  the  slim,  strongly  moving  larvae  are 
placed  on  moistened  earth  they  continue  their  development  and  she 
has  been  able  to  raise  eleven  successive  free-living  generations  in  this 
way. 


i  Von  Linden,  Grafin.  Untersuchungen  iiber  die  Entwickelung  der  f  reilebenden 
Generationen  der  Lungenwiirmer.  Centralblatt  fiir  Bakt.,  Parasit.,  und  Tnfekt. 
Orig.  Bd.  76,  Nr.  2-3,  pp.  ] 47-178  (20  May,  1915). 


6 


Dr.  von  Linden  believes  that  the  embryos,  intended  to  reproduce 
the  free  living  generations,  work  their  way  up  the  trachea  and  are 
swallowed  and  excreted  from  the  body  with  the  feces.  The  embryo 
then  molts  and  withdraws  within  its  cast  skin,  which  forms  a  sort  of 
cyst,  protecting  the  larva  from  extremes  of  heat  or  cold  and  dryness 
until  conditions  are  suited  to  its  growth.  Under  favorable  conditions 
the  second  generation  of  worms  appears  in  from  four  to  six  weeks  and 
further  generations  continue  to  appear  at  this  interval  for  about  four 


Goat  infested  with  lungworms  being  treated  with  chloroform 
by  means  of  a  bulb  pipette. 


months.  This  period  of  increase  is  generally  followed  by  a  standstill 
of  about  three  months  when  the  period  of  increase  again  starts.  The 
thick,  slow-moving  embryos  die  almost  immediately  when  placed  out- 
side the  body. 

The  presence  of  this  free-living  type  of  the  parasite  discovered  by 
Dr.  von  Linden  and  partly  confirmed  by  our  own  observations,  would 
explain  the  major  part  of  the  hitherto  unknown  life  history.  Experi- 
ments attempting  to  confirm  and  duplicate  Dr.  von  Linden 's  work  are 
now  under  way. 


Accepting  the  presence  of  a  free  living  generation  there  remains 
only  one  dark  point  in  the  life  history.  That  is  the  method  by  which 
stock  becomes  infested.  The  most  logical  method  would  seem  to  be 
that  the  larvae  find  their  way  into  the  nostrils  from  the  ground  or  are 
snuffed  up  as  encysted  larvae  in  dust,  for  the  larvae,  when  subjected 
to  excessive  dryness,  are  said  to  encyst  within  their  cast  skins.  The 
other  belief  is  that  they  are  swallowed  and  burrow  their  way  through 
some  point  in  the  alimentary  canal  and  are  carried  thence  to  the  lungs. 

Epidemiology. — The  epidemiology  and  the  control  are  so  closely 
linked  that  the  history  of  two  typical  cases  that  have  come  under  the 
writers'  observation  are  included. 

The  angora  goats  mentioned  above  contracted  the  infestation  prac- 
tically simultaneously  when  pastured  on  a  range  free  from  other 
domesticated  animals  and  where  lungworms  had  not  previously  been 
observed.  They  were  purchased  from  a  flock  free  from  lungworm  and 
transported  directly  to  their  pasture.  Deer  were  prevalent  in  that 
part  of  the  country  and  some  were  shown  to  be  infested  with  the  same 
species  of  lungworm  (D.  filaria),  that  the  goats  contracted.  .Deer 
were  seen  to  use  the  same  drinking  places  frequented  by  the  goats  and 
hence  the  logical  conclusion  was  that  the  goats  became  infested  from 
the  deer. 

Another  instance  showed  four  calves  which  had  been  placed  on  a 
heavy  clover  pasture  directly  after  weaning.  This  farm  had  a  history 
of  lungworm  the  year  before.  In  about  four  months  all  four  calves 
became  infested.  Their  pasture  was  open  to  no  other  animals,  but 
they  used  the  common  drinking  trough  with  the  other  farm  animals. 
Cows  are  known  to  harbor  lungworms,  which,  however,  never  cause 
any  indisposition  in  these  adult  animals, — calves  alone  being  seriously 
affected.  It  seems  in  this  case  as  though  an  adult  carrier  may  have 
been  the  source  of  the  infestation,  or  more  probably,  according  to  von 
Linden,  the  infection  was  due  to  the  free  living  type  of  the  parasite 
which  had  been  reproducing  in  the  moist  parts  of  the  pasture. 

Prophylaxis. — Regardless  of  the  mode  of  infestation,  the  essential 
factor  is  to  build  up  the  general  health  of  the  stock,  providing  abund- 
ant food  and  proper  shelter  in  order  that  they  may  resist  any  infesta- 
tion of  the  parasites. 

Infested  animals  should  be  isolated  and  all  excrement  from  them 
should  be  properly  sterilized.  Healthy  animals  should  not  be  quar- 
tered on  pastures  known  to  have  a  definite  history  of  lung-worm 
infestation.  Animals  pastured  on  low,  wet  ranges  become  infested 
more  readily  than  those  on  dry  locations.  If  practical,  measures 
should  be  taken  to  control  possible  carriers,  cows  and  deer. 


SUMMARY 

1.  Verminous  bronchitis  is  caused  by  an  infestation  of  nematode 
worms  known  as  lungworms,  each  species  of  which  has  a  favorite  host, 
to  which,  however,  it  is  not  obligatory. 

2.  Other  investigators  have  demonstrated  free  living  generations 
of  these  worms  which  are  capable  of  reproducing  in  moist  soil  and 
which  are  able  to  withstand  drying  in  an  encysted  state. 

3.  Treatment  by  nasal  injections  of  chloroform  in  amounts  varying 
with  the  general  condition  of  the  animal,  followed  by  a  saline  purge 
and  feces  sterilization,  has  proved  very  successful. 

4.  Deer  and  possibly  cows  may  act  as  carriers  and  should  be  ex- 
eluded  from  the  pasture  land  of  susceptible  stock. 

5.  The  general  health  of  the  stock  is  a  determining  factor  in  re- 
sisting an  attack  of  the  parasites.  Every  care  should  be  observed  to 
insure  plenty  of  food  and  proper  shelter. 


